238 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25, 



equivalents of the Bognor beds more difficult than with the preceding 

 division. 



In the third division of his first group of ' Sables inferieurs * M. 

 d'Archiac places an irregular and variable deposit, termed by him 

 ' Gres et poudingues,' and consisting of siliceous sands, imperfect 

 sandstones and pebble beds, which immediately overlie the * Argile 

 plastique ' and lignites. These conglomerate beds are overlaid suc- 

 cessively by three other divisions, which complete his first group of 

 the Eocene strata, a group succeeded by the 'Glauconie grossiere' and 



* Calcaire grossier,' which he places in his second group (section p. 

 234-). The three divisions above named he terms, in ascending order, 



* Sables divers,' * Lits coquilliers,' and ' Sables et glaises.' They 

 consist of a very irregular mixture of siliceous and calcareous sand, 

 concretions and imperfect earthy impure limestones, with frequent 

 greensands and a good deal of clay. These beds pass one into 

 another, rarely occur together, and are very irregular in their range 

 and thickness. Taking the base of the Bognor beds as the diverging 

 point in the mineral composition of the Paris with the Hampshire 

 and London basins, it will be observed, that in the ascending series 

 calcareous sands and limestones predominate in France, and argilla- 

 ceous beds in England. It is not however until a later period that 

 the lithological characters present their greatest dissimilarity. 



The four above-mentioned divisions (3 to 6, section p. 234) of 

 M. d'Archiac's lowest Eocene group do not hold in the English 

 series ; but it is probable that taken together they are represented 

 partly by the Bognor beds. This appears to be the case for several 

 reasons. In the first place the superposition is in the same order. 

 Secondly, the commencement of both series indicates some change 

 and disturbance in the Eocene seas. Thirdly, some similarity of 

 mineral structure is traceable, and this in a somewhat marked manner, 

 since the calcareous and sandy character of these beds at Bognor is 

 well-known, and at White Cliff Bay they contain much greensand ; 

 whilst in France, in contrast with the general character of the French 

 marine Eocene strata, they are also much mixed with greensands, yel- 

 low and brown clays, which frequently form compact and tenacious 

 beds, and give rise to numerous springs from the percolation of water 

 through the sands and limestones of the calcaire grossier. It is also 

 probable, fourthly, by the analogy of organic remains ; for notwith- 

 standing that the fauna of the Bognor beds in England is very limited 

 in species, it everywhere presents a very typical and constant group 

 of fossils. In France the series is more developed than in England, 

 and the organic remains are confined almost exclusively to the 5th 

 division, viz. the ' Lits coquilliers,' a deposit almost as rich in fossils 

 as the calcaire grossier. Most of the species are the same as those 

 found in the calcaire grossier ; but those which are distinct are in 

 sufficient number to entitle the bed to be considered as a separate 

 division. M. d'Archiac* enumerates 197 species from the 'Lits 

 coquilliers,' and describes twenty seven of them as characteristic of 



* JNIem. de la Soc. Geol. de France, vol. v. p. 268. 



